Regional analysis of bin aeration as an alternative to insecticidal control for post-harvest management of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.)

The objectives of this study are to 1) develop an integrated aeration and insect pest modeling system and 2) determine the potential of aeration in controlling rice weevil, Sitophilus oryzae (L.), and lesser grain borer, Rhyzopertha dominica (F.), as an alternative to the use of insecticides. Grain temperature, moisture, and pest population dynamics were simulated at each layer and radial position within a storage bin using a two-dimensional aeration model coupled with an age-structured distributed-maturation insect population model. The models were parameterized and validated using data from the literature and controlled experiments. Regional analysis across major U.S. rice states suggests adult populations of both species decrease progressively towards higher latitudes mainly due to lower fall and winter temperatures, with much lower populations for lesser grain borer than for rice weevil. Increasing the target temperature for storage bin aeration from 7.2°C to 15.6°C more than doubled the adult populations in the southern states, but the effect in the more northerly rice states was much less due to ambient air temperatures seldom reaching the target temperature. An increase in aeration airflow rate from 0.69 to 1.38m3/min/MT (metric ton) had a much greater impact in reducing adult populations than a decrease in the aeration target temperature. Weather variation between years within a county greatly impacted pest populations. Even in the southern states, predicted rice weevil populations under aeration exceeded 1000 adults/MT in less than half of the years. These results highlight the site-specific impact of aeration on S. oryzae and R. dominica and the need to develop cost-effective site-specific aeration and insect pest management strategies.